Buy a new turbo from protegegarage.com Ken will hook you up just give him a call. And IDK what your knowledge of the MSP and it's drivetrain is...but I doubt the MSP would like a STI turbo. I imagine it's larger, and the MSP's toothpicks for rods wouldn't like that very much.
Then even if you do pick up the STI turbo you will basically be buying a whole new turbo setup, because you will need manifold, oil lines, downpipe, etc, etc. Not to mention tunning for that setup.
IMO I wouldn't even consider it.